KR20090105489A - Highly flame-retardant, halogen-free heat-shrink tubing and resin composition for the same - Google Patents

Abstract

PURPOSE: A highly flame-retardant, halogen-free heat-shrink tube is provided to ensure good fire retardancy, excellent expansion workability due to low tensile modulus, and low loss of mechanical property. CONSTITUTION: A highly flame-retardant, halogen-free heat-shrink tube comprises: 100 parts by weight of a base resin consisting of a ethylene-vinyl acetate copolymer; 100 ~ 150 parts by weight of metal hydroxide flame retardant; and 1 ~ 10 parts by weight of flame retardant aid. The base resin is an ethylene-vinyl acetate copolymer in which the ratio of the acetic acid vinyl monomer is 15 ~ 33%.

Description

High flame retardant non-halogen heat shrink tube and resin composition therefor {HIGHLY FLAME-RETARDANT, HALOGEN-FREE HEAT-SHRINK TUBING AND RESIN COMPOSITION FOR THE SAME}

The present invention relates to a non-halogen flame retardant heat shrink tube and a resin composition therefor. More specifically, the present invention relates to a resin composition for a heat shrinkable tube and a heat shrinkable tube in which a polymer resin having a low tensile modulus at a high temperature is used, and an inorganic flame retardant and a flame retardant aid are properly mixed to balance expansion processability and flame retardancy.

The heat shrink tube is a tube having a property of shrinking its diameter or length after heating, and is also used for packaging by tightly covering a connection part such as a coated wire or a pipe or being inserted into the outer peripheral surface of a bottle or a battery. In a widely used method of manufacturing a heat shrink tube, the thermoplastic resin is first extruded, and then the inserted thermoplastic resin is crosslinked using a method such as electron beam irradiation. The crosslinked resin is then heated to a temperature above its crystal melting temperature to expand and then cooled to prepare the final product.

Conventional heat shrink tubes are not suitable for high flame retardant non-halogen heat shrink tubes because they mainly use polyvinyl chloride (PVC) or bromine and antimony flame retardants. PVC is characterized by excellent water resistance, chemical resistance, flame retardancy, etc., but when incomplete combustion, pollutant dioxin is generated, causing environmental pollution. Therefore, the recent trend is to regulate the use of PVC. Halogen-based flame retardants, including bromine-based, also has the advantage of exhibiting high flame retardancy even in a small amount, it causes environmental problems, due to safety, such as the generation of toxic gases during combustion is regulated.

For this reason, efforts have been made in this field to find other flame retardant polymer materials for heat-shrinkable tubes. For example, Korean Patent Publication No. 1999-1771 discloses a metal hydroxide, a copolymer of linear low density polyethylene and ethylene-vinyl acetate. Introduced flame retardant and low flame retardant tubes with excellent drop characteristics by adding decabromodiphenyl oxide and antimony trioxide.However, a large amount of die drool may occur during tube extrusion, which may cause product defects. This is the cause that can not proceed.

In particular, in the case of the heat shrink tube, the expansion process is necessarily included, unlike the conventional wire manufacturing process, there is a serious problem that the expansion process itself is impossible if a large amount of metal hydroxide flame retardant is used to secure sufficient flame retardancy. Moreover, the thickening of the heat shrinkable tube doubles the difficulty because the heat shrinkage tube has a larger amount of heat to be applied in the expansion process than the non-thick heat shrinkable tube. For this reason, the large diameter heat shrinkable tube containing an inorganic flame retardant in 150 weight part or more is very difficult to manufacture by a conventional technique.

Therefore, the composition for the non-halogen-type heat-shrinkable tube having sufficient flame retardancy has good mechanical properties and excellent expansion processability, and the heat-shrinkable tube using the same remains a problem in the industry.

SUMMARY OF THE INVENTION The technical problem of the present invention is to develop a resin composition for a heat shrinkable tube which enables the production of a highly flame retardant large diameter heat shrinkable tube with good expansion processability as a polymer resin composition for a highly flame retardant heat shrinkable tube containing no halogen component.

In order to achieve the above object, the resin composition for heat shrinkable tubes of the present invention comprises 100 to 150 parts by weight of a metal hydroxide flame retardant and 1 to 10 parts by weight of a flame retardant aid based on 100 parts by weight of a basic resin composed of an ethylene-vinyl acetate copolymer. It is done by In this case, the basic resin is characterized by being an ethylene-vinyl acetate copolymer having a melt index of 2 to 15, which is polymerized by setting the proportion of the vinyl acetate monomer to 15 to 33% by weight.

As a flame retardant of the resin composition for heat shrinkable tubes of this invention, magnesium hydroxide surface-treated with vinyl silane is suitable, and red phosphorus is preferable as a flame retardant adjuvant.

The resin composition for a heat shrinkable tube of the present invention may further include an antioxidant, a lubricant and a crosslinking aid in addition to the above components.

The present invention also provides a heat shrink tube produced using such a composition for heat shrink tubes.

The heat shrink tube manufactured using the resin composition for heat shrink tubes of the present invention has excellent tensile workability due to low tensile modulus at high temperature. In addition, the flame retardancy is good without using a halogen stabilizer, the loss of mechanical properties is useful as a general non-halogen high flame-retardant heat shrink tube, and is particularly suitable for high flame-retardant large diameter heat shrink tube applications.

The flame retardant resin composition for a heat shrinkable tube of the present invention is prepared by including a metal hydroxide flame retardant and a flame retardant aid based on an ethylene-vinyl acetate copolymer.

The base resin of the composition according to the invention is a copolymer of ethylene-vinyl acetate (EVA). EVA copolymer resin has the same flexibility and rubber elasticity as soft PVC, has excellent molding processability, resists cracking by stress, and is hygienic and non-toxic. Since the EVA resin can adjust the physical properties according to the content of vinyl acetate (VA), when used as a material of the heat shrink tube, flexibility and strength can be appropriately harmonized.

In the basic resin of the present invention, an ethylene-vinyl acetate copolymer polymerized using a vinyl acetate (VA) monomer content of 15 to 33 wt% is used. Since the ethylene-vinyl acetate copolymer resin has a low melting point and a relatively high content of vinyl acetate, the flexibility is large, and thus the tensile modulus at high temperature can be kept small. In case of using EVA resin with vinyl acetate monomer content less than 15% by weight, the modulus becomes large due to lack of flexibility, and when EVA resin is used in excess of 33% by weight, the strength is insufficient to satisfy the specification of heat shrink tube. I can't.

And the EVA resin uses a melt flow index (melt flow index) of 2 to 15 g / 10 minutes. The heat shrink tube made of EVA resin having a melt index of less than 2 has the disadvantage of increasing the high temperature modulus due to the poor flow of the resin, and the heat shrink tube having a melt index exceeding 15 has a problem that extrusion is impossible due to high flowability. Because it is not desirable.

The resin composition for a heat shrinkable tube of the present invention contains 100 to 150 parts by weight of a metal hydroxide flame retardant and 1 to 10 parts by weight of a flame retardant aid based on 100 parts by weight of the base resin for flame retardancy.

As the metal hydroxide flame retardant of the present invention, magnesium hydroxide or aluminum hydroxide is suitable, and surface treated is more preferable. As the surface treatment material, vinyl silane is preferred. When the content of the metal hydroxide flame retardant is less than 100 parts by weight, the flame retardancy is insufficient, and when it exceeds 150 parts by weight, the modulus rises and the expansion process becomes impossible, which is not preferable.

Examples of the flame retardant aids paired with the metal hydroxide flame retardant include red phosphorus. If the content of the flame retardant aid exceeds the upper limit, the appearance of the product is poor, which is not preferable, and if it is less than the lower limit, it becomes difficult to exhibit sufficient flame retardancy.

The composition for producing a flame-retardant heat-shrink tube according to the present invention may include any one material selected from an antioxidant, a crosslinking aid, and a lubricant, or two or more materials. Antioxidants protect physical properties by preventing air oxidation of polymer resins that occur at high temperatures. As the antioxidant of the present invention, it is preferable to use any one selected from the group of thioester-based and phenol-based materials or a mixture of two or more selected from them. A specific example is A / O 1010. In the present invention, the antioxidant is included in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the base resin.

As the crosslinking aid of the present invention, it is preferable to use a trimethacrylate-based material. As a specific trimethacrylic acid-based material, trimethylol trimethacrylate is preferable. In the present invention, the crosslinking aid is included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the polyester base resin. In the case of below the lower limit, the effect of the addition of the crosslinking aid is insignificant, and in the case of exceeding the upper limit, the initial crosslinking reaction rate is rapidly increased, thereby increasing the crosslinking degree to produce a heat shrinkable tube. The problem arises that the expansion process, which is part of the process, becomes impossible.

In the present invention, it is possible to increase the release property from the metal surface and suppress the generation of frictional heat during the production of the heat shrinkable tube by using a lubricant. There are no particular limitations on the lubricants that can be used in the resin composition of the present invention, and any lubricants commonly used in the art may be used. Some examples include stearic acid, stearyl alcohol, butyl stearate, waxes, and the like. If the lubricant content is less than 0.5 parts by weight, there is no lubricating effect, and if it exceeds 10 parts by weight, the physical properties of the entire resin composition may be impaired, such as kneading becomes difficult, which is not preferable.

In addition, the composition for producing a heat shrinkable tube according to the present invention may further include various functional additives commonly used in the resin composition within a range that does not impair the effects of the present invention. Such additives include sunscreens, heat stabilizers, lubricants, antiblocking agents, antistatic agents, waxes, coupling agents, pigments, and the like, although not illustrated, various kinds of materials may be selected and used as necessary.

In this invention, the heat shrink tube manufactured using the said resin composition for heat shrink tubes is also provided. 1 is a cross-sectional view of a heat shrink tube 10 for explaining an embodiment according to the present invention. As shown in FIG. 1, it can be seen that the tube consists of an outer shell layer 12 having a hollow portion 14 therein. The resin composition of the present invention can be used to prepare heat shrink tubes in various forms according to well known heat shrink tube manufacturing methods. That is, the resin composition of the present invention is extruded to produce a pipe having a desired diameter size, and the pipe is chemically treated or crosslinked using an electron beam or the like. The crosslinked pipe is heated to a temperature above the crystal melting temperature, and then the expanded heated pipe is expanded by the shrinkage of the resin measured in advance. In addition, the expanded pipe is cooled and cut to size to obtain various heat shrink tubes.

The resin composition for flame retardant heat shrink tube according to the present invention has a low temperature tensile modulus, which facilitates an expansion process, and has good flame retardancy, which is useful for non-halogen heat shrink tube, and has the advantage of making a large diameter flame retardant heat shrink tube.

< Example >

The present invention will be described in more detail with reference to the following Examples. The average person skilled in the art to which the present invention pertains may change the present invention in various other forms in addition to the embodiments described in the following examples, and the following examples merely illustrate the present invention, and the scope of the technical spirit of the present invention is given below. It is not to be construed as limiting the scope of the examples.

In order to examine the performance change according to the composition of the resin composition for heat shrinkable tube of the present invention, the flame retardant resin compositions of Comparative Examples and Examples were prepared with the compositions shown in Table 1 below. All units in Table 1 are parts by weight, and component values deviating from the composition of the resin composition for a heat shrinkable tube according to the present invention are shown in bold italics .

 Composition (parts by weight)  Example  Comparative Example One 2 3 One 2 3 EVA resin 1 (VA 28 wt%, paper index 4)  100  ―  100  ―  100  100 EVA resin 2 (VA 28% by weight, Solvent index 15)  ―  100  ―  ―  ―  ― EVA Resin 3 (VA 25 wt%, Solvent Index 1.0 )  ―  ―  ― 100  ―  ― Metal Hydroxide Flame Retardant ^* 120 120 150 120 85 120 Flame Retardant Supplements ^** 2.5 2.5 2.5 2.5 2.5 0 Antioxidant ^† 3 Crosslinking aids ^‡ 3

Magnesium hydroxide surface treated with stearic acid

** red phosphorus

† Irganox 1010 (Ciba Speciatly Chemicals), a high molecular weight hindered phenolics antioxidant

‡ the SR-350 trimethylolpropane trimethacrylate (trimethylolpropane trimethacrylate) (Sartomer社)

Comparative Examples and Examples described in Table 1 differed only in the vinyl acetate (VA) content and the melt index of the ethylene-vinyl acetate (EVA) resin used, but the content and the remaining components were the same or similar. Among the EVA resins of Table 1, 1 and 2 satisfy the vinyl acetate content and the melt index according to the present invention, and EVA resin 3 is a case where the melt index is less than the lower limit of the present invention.

Property measurement and evaluation

Each specimen heat shrink tube was prepared as follows using the composition according to Examples (1 to 3) and Comparative Examples (1 to 3).

Each composition was kneaded at 120 DEG C for 10 minutes using a roll mill, and then the specimen was prepared by post-treatment by pressurizing at 170 DEG C for 20 minutes for chemical crosslinking.

Flame retardant test samples were prepared on sheets of 1 mm and 3 mm to evaluate physical properties.

The tensile modulus and flame retardancy test results at high temperatures for the Example and Comparative Example specimens thus obtained are summarized in Table 2 below. Brief experimental conditions are as follows.

㉠ high temperature tensile modulus

Preheat the specimen in the oven to 170 ° C for 6 minutes corresponding to the expansion process conditions of the heat shrink tube, then measure the tensile strength and record the tensile strength at 15% elongation. From this the tensile modulus is calculated. Of 10 kg / mm ² based on tensile modulus of heat shrink tubing products If it has the following values, it determines with pass.

㉡ flame retardant

Vertical flame retardancy tests were performed in accordance with the criteria set by the US Department of Defense MIL-23053.

Example Comparative Example One 2 3 One 2 3 High temperature modulus (standard: 10 kg in / mm ² or less) 7.4 kg / mm ² 6.3 kg / mm ² 8.7 kg of / mm ² 13.8 kg / mm ² 5.4 kg / mm ² 7.4 kg / mm ²  Vertical flame retardancy pass pass pass  pass  fail  fail

As a result of measuring the physical properties as summarized in Table 2, both the flame retardancy and the high temperature tensile modulus satisfy the reference values, and the appearance and the extrudability were excellent. However, Comparative Example 1, which consists of EVA resin 3 in which the melt index differs slightly from the EVA resin used in Examples, did not meet the standard in terms of high temperature tensile modulus. This is a result that the EVA resin melt index value of Comparative Example 3 is out of the melt index numerical limitation range according to the present invention.

In addition, it was confirmed from the flame retardant test results of Comparative Examples 2 and 3 that the flame retardancy does not meet the specifications when the content of the metal hydroxide flame retardant and the flame retardant auxiliary agent according to the present invention is not observed.

As seen from the above results, the flame-retardant resin composition for heat-shrinkable tubes of the present invention has a low tensile modulus of resin and is excellent in flame retardancy to help manufacture a heat-shrinkable tube having good expansion processability and flame retardancy.

As described above, optimal embodiments of the present invention have been disclosed. Although specific terms have been used in the specification including this embodiment, it is used only for the purpose of describing the invention in detail to those skilled in the art and used to limit the meaning or limit the scope of the invention described in the claims. It is not.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings attached to the present specification illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, the present invention is intended to help understand the technical idea of the present invention. No.

1 is a cross-sectional view of a flame retardant heat shrink tube 10 for explaining an embodiment according to the present invention.

<Description of main parts of drawing>

10 tube 12 outer layer 14 hollow part

Claims (9)

100 parts by weight of a basic resin consisting of an ethylene-vinyl acetate copolymer; 100 to 150 parts by weight of the metal hydroxide flame retardant; And It comprises 1 to 10 parts by weight of flame retardant aids, The basic resin is an ethylene-vinyl acetate copolymer having a melt index of 2 to 15, polymerized using a vinyl acetate monomer in a proportion of 15 to 33% by weight, and the resin composition for a heat shrinkable tube. The method of claim 1, The said metal hydroxide flame retardant is magnesium hydroxide, The resin composition for heat shrink tubes. The method of claim 2, The said magnesium hydroxide was surface-treated with vinyl silane, The resin composition for heat shrink tubes. The method of claim 1, The flame-retardant auxiliary agent is a red phosphorus (赤 燐), the resin composition for heat shrink tube. The method of claim 1, The resin composition for a heat shrink tube further comprises one or two or more additives selected from the group consisting of antioxidants, crosslinking aids and lubricants. The method of claim 5, The antioxidant is any one or a mixture of two or more selected from a thioester-based material and a phenol-based material, 0.5 to 10 parts by weight based on 100 parts by weight of the base resin, characterized in that the resin composition for a heat shrinkable tube. The method of claim 5, The crosslinking aid is a trimethacrylate-based material, 1 to 10 parts by weight based on 100 parts by weight of the base resin, the resin composition for a heat shrinkable tube. The method of claim 5, The lubricant is 0.5 to 10 parts by weight based on 100 parts by weight of the base resin, the resin composition for heat shrink tube. A heat shrink tube, which is prepared using the resin composition for heat shrink tube selected from claim 1.

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